I think ideal weight for the areas you indicate would be 5wt. I just think a 4 is a little light for streamers on the Bow, and I would worry a bit about the frequent southern Alberta winds. I have a 5 and 6 (plus 8) and would love to have a 3 or 4, but not as my
only rod. Now if you got the 4 and then picked up a 6, I think that would be perfect.
Now go ask someone who is a GOOD fisherman